The overall goal of this project is to (a) investigate the possible role of adjunctive medical therapy that would improve stone removal following extracorporeal shock wave lithotripsy and (b) more clearly define the role of specific medical therapy of nephrolithiasis after lithotripsy treatment. Two clinical studies have been defined and are grouped into two specific aims. The first aim will determine whether potassium magnesium citrate (K-Mag) treatment would facilitate stone passage, alleviate "steinstrasse" (obstruction of the ureter with stone fragments) and reduce residual stone mass following extracorporeal piezoelectric lithotripsy (EPL). The proposal will test the hypothesis that K-Mag treatment would meet the above expectations, by raising urinary magnesium and citrate levels. The rise in these "inhibitors" in urine would prevent agglomeration of stone fragments. Moreover, the complexation of calcium by citrate and that of oxalate by magnesium may lead to a reduced stone mass. The above action's may be exaggerated by an increase in urinary pH occurring from K-Mag therapy. The overall goal of the second aim is to conduct a randomized prospective trial to determine the role of specific medical therapy in the management of symptomatic renal calculi following lithotripsy and to ascertain if there are any long-term adverse effects (hypertension, diminished renal function, stone recurrence, etc) following stone removal by extracorporeal shock wave lithotripsy. It is hypothesized that patients with symptomatic calculi will respond well to selective medical therapy following extracorporeal shock wave Iithotripsy and may not require additional lithotripsy procedures due to adequate control of their metabolic stone disease. Moreover, it is speculated that the long-term adverse effects of Iithotripsy such as hypertension and reduced renal function are probably infrequent occurrences.